Method of selective electrical tuning



March 18, 1930. uss 1,750,660

METHOD OF SELECTIVE ELECTRICAL TUNING Original Filed Nov. 4, 1924 a Sheets-Sheet 1 d A220 ne March 18, 1930. H. N. BLISS 1,750,660

METHOD OF SELECTIVE ELECTRICAL TUNING Original Filed Nov. 4, 1924 3 Sheets-Sheet 2 i lhlili Iii? Qlllll! INVENTOR March 18, 1930. H. N. Buss METHOD OF SELECTIVE ELECTRICAL TUNING Original Filed Nov. 4, 1924 3 Sheets-Sheet 3 R o T N E V N Patented Mar. 18, 1930 UNITED STATES HAROLD N. BLISS, OF ITHACA, NEW YQRK METHOD OF SELECTIVE ELECTRICAL TUNING Original application filed November 4, 1924, Serial No. 747,846. Patent No. 1,588,438. Divided and this application filed May 18, 1926.

My invention relates broadly to systems of electrical tuning, and more particularly to a method or system for selectively tuning a plurality of electrical circuits to resonance by means of a single manual control.

This application is a division of my application Serial Number 747,846, filed November 4, 1924, now Patent No. 1,588,438.

One of the objects of my invention is to provide a method by which a plurality of electrical circuits, each of which having inherently different characteristics, may be tuned to resonance at the same frequency for the efficient transfer of energy from one circuit to the other at a selected frequency.

Another object of my invention is to provide a system of electrical tuning by which a series of electrical circuits may be simultaneously adjusted to resonance at a particular frequency from a single control with means for automatically compensating for electrical differences which may exist between the several circuits whereby energy at the selected frequency may be efficiently trans ferred from one circuit to another.

Still another object of my invention is to provide a system of electrical tuning by which a series of electrical circuits having relatively different characteristics may be simultaneously adjusted to resonance at selected frequencies with means capable of imparting irregular motion to the various variable members of the circuits, this motion be ing so proportioned as to compensate for the electrical differences in the several circuits whereby energy at the selected frequency may be efficiently transferred from one circuit to another.

My invention will be more fully understood from the specification hereinafter following by referenceto the accompanying drawings, in which:

F igure 1 is a rear view of the condenser construction employed in the circuit arrangement of my invention showing the method of varying the angular position of two sets of stator plates simultaneously with the change in position of the rotor plates; Fig. 2 is a cross-sectional view taken through the con- Serial No. 109,902.

denser illustrating the rotatable shaft and I the arrangement of the sets of rotor plates and corresponding sets of stator plates; Fig. 3 is a vertical cross-sectional View taken through the condenser along line 3-3 of Fig. 1 showing the arrangement of the rotor plates and one set of the stator plates illustrating the mechanical interlinkage between the cam on the rotor shaft and the rocker arm on one of the stator shafts; Fig. i is a side view of the assembled condenser; Fig. 5 represents the circuit arrangement employed in my method of selective electrical tuning of a radio receiving circuit; Fig. 6 is a perspective view of one of the insulating bushings employed for the support of the stator plates; Fig. 7 is a detail View of the shaft construction for the stator plates showing the connection of the rocker arm with the shaft; and Figs. 8 and 9 are partial crosssensitive radio receiving apparatus it has been necessary to selectively tune the input circuits of a plurality of electron tubes connected in cascade. Owing to the extreme difficulty in commercial practice of balancing various parts of a plurality of tuned circuits to enable their adjustment by means of a single control, I have found it desirable to provide a tuning element having a compensating device actuated by the single control capable of correcting wide differences in the various tuned circuits thereby obviating careful balancing of these circuits. The adjustment of these several condensers is often tedious and requires careful manipulation by an experienced operator. The several adj usting devices must be individually adjusted to a nicety in order to place the several circuits in a condition of resonance. Complications often arise by reason of lack of adjustment of any one of the several adjusting devices, rendering the circuits inefficient or totally inefiective for a desired signal. By my present invention I provide a method for selective electrical tuning by means of a single control. In the apparatus employed in carrying out the tuning method of my invention I provide a rotor having a plurality of sets of laterally projecting plates and a corresponding number of sets of stator plates for cooperation therewith, the sets of plates being connected in shunt with the several circuits which are to be selectively tuned to a given signaling frequency. I find that it is necessary to compensate for differences which exist in the several electrical circuits and I therefore provide means for mechanically changing the angular position of the stator plates with respect to the rotor plates simultaneously with the rotation of the rotor plates. I employ a cam mechanism for this purpose arranged to cooperate with the rocker arms upon which are mounted the stator plates whereby the rotor plates may be moved between the stator plates and differences in the electrical circuits in which the sets of rotor and stator plates are included compensated for by angular movement of the stator plates. By means of a single control a plurality of electrical circuits may be adjusted simultaneously by the apparatus as herein described.

Referring more particularly to the drawings, reference character 1 designates the rear supporting plate for the multiple automatic condenser, while reference character 2 shows a front supporting plate. The plates are connected together by means of standards 3, 4, 5, 6, 7, and 8, disposed about the periphery of front and rear plates 1 and 2. A bearing 9 is carried by plate 2 and a bearing 10 by plate 1 aligned therewith in which the shaft 11 is journaled. The shaft 11 has spacer members 12 carried thereon with the rotor 20 having plates 21, 22 and 23 spaced one from another thereon by means of the spacing members 12 which serve as separators. The plates are secured in position on the shaft 11 by means of a nut 14 at one end and a spacing member 16 at the other end which engages shoulder 17 of the shaft 11 and bears against the bearing 10. The securing member 14 is held in posi tion by means of a resilient yoke device 15 which bears on the flat surface of the member 14 and constantly urges the shaft in the direction of bearing 10. The shaft 11 is provided with a screw threaded end 18 upon which the cam 19 is secured by means of a nut or other suitable securing device. The cam 19 has a substantially semi-circular edge face cut in a manner determined by the electrical characteristics of the circuits with which the multiple automatic condenser is employed as will be hereinafter described in more detail. The stator plates for the condenser are shown at 24, 25 and 26 carried by shafts 43, 28 and 42, respectively. The stator plates 24 are permanently located in position by means of adjustable set screws 44 in end plate 2 and the nut in end plate 1. The shafts 28 and 42 are arranged to rock or have angular movement in either direction. Figure 3 illustrates the arrangement of the angularly movable plates. Shaft 28 is counter-sunk at the end 32 into which the adjustable screw 33 centers.

A shoulder 34 is provided on the shaft 28 and bears against the end plate 1 carrying thereon the insulated bushings 29 and 30 securing the stator plates 25 and separator members 31 in position on the shaft. The shaft 28 projects through the end plate 1 as indicated at 35 and carries thereon a rocker arm or lever 36 having an end 37 bent toward the cam face 19 and arranged to engage and ride upon the edge thereof rocking the shaft 28 in accordance with the angular movement of lever 36. Similarly the stator plates 26 on shaft 42 are provided with a rocker arm 38 connected to an extension 41 of the shaft 42. The rocker arm 38 has an end 39 directed in the direction of the end 37 and arranged to engage the edge surface of cam 19. The rocker arms 36 and 38 are constantly drawn toward each other by means of a spring 40 and the operation of the cam 19 is such that it tends to move the rocker arms 38 and 36 apart against the action of spring 40. The terminals for the condenser are formed by the rotor shaft 11 and each of the sets of stator plates 24, 25 and 26 as represented by the extension member 58 on the set of stator plates 25. It will be observed that the entire set of stator plates 26 are arranged to be rocked in the construction illustrated in Figs. 2 and 3. I may also provide a construction as illustrated in Fig. 8 wherein a single stator plate 55 is rocked upon movement of cam 19 and lever arm 38. In this arrangement the stator plates 26 pass between'rotor plates 23 and are carried on insulated bushings 29 and 30 and spaced by separators 31. The bushings 29 and 30 are disposed upon a tubular member 57 forming a ournal for a shaft 50. The stator plates 26 are spaced with respect to the end plates 1 and 2 by means of spacer members 53 and 54 with the shaft passing through the bearing 57 and being secured by spring washer 51 retained under tension by means of nut 52. The shaft 50 is provided with an annular journal 49 which bears against member 57 forming a bearing surface therewith. The extension 47 of the shaft 50 is screw threaded as represented at 58 enabling spacing member 53 to be secured thereon, which member also serves as a bearing member. Insulated washers 54 and 56 are gripped between the shoulder 49 of the spacing member 53, locking plate rigidly with respect to shaft 50 whereby plate 55 may be rocked between plates 47 of the rotor. The

plates 47 of the rotor are spaced from the other plates of the rotor by means of a spacing washer 46. Connection is made from stator plate with stator plates 26 and with an exterior circuit through projecting lugs on the plates and a flexible connection indicated at 58.

The operation of the multiple automatic condenser will be understood from the description given hereinbefore. The application of the apparatus to a radio receiving circuit is illustrated more clearly in Fig. 5 wherein an antenna ground system is represented at and 61. A tuning transformer 62 is employed in the system with a primary winding 63 and secondary winding 64 in connection therewith. An electron tube 65 is connected to function as a amplifier of radio frequency energy. A transformer 66 has its primary 67 connected in the output circuit of electron tube 65 and its secondary winding 68 connected in the input circuit of tube 70 which is also arranged to function as a radio frequency amplifier. Radio frequency transformer 71 is provided with its primary 72 connected in the output circuit of tube 70 and its secondary winding 73 connected in the input circuit of a tube detector 74. A responsive device 7 5 may be connected in the output circuit of the detector or a plurality of stages of audio frequency amplification may be employed. The filaments of all of the electron tubes may be supplied from battery 76 While the plate potential for the several tubes is supplied from battery 77. The rotor plates 21, 22 and 23 are connected to one side of each of the secondary windings 64, 68 and 7 3 of radio frequency transformers 62, 66 and 71 respectively. The stator plates 24, 25 and 26 are respectively connected with the opposite side of secondary windings 68, 73 and 64. The cam 19 is so arranged that uponmovement of the rotor shaft the sets of stator plates may be individually rocked to compensate for the electrical differences in the several electron tube circuits as the rotor plates are interleaved between the set-s of stator plates.

I am aware that cam drives have been used, but in such devices, the cam has been shaped to provide the major tuning over the whole broadcast range as well as the microcorrectional tuning of the individual elements, and has been incapable of the high degree of correctional precision characteristic of my method. My invention is distinguished from such devices in that they derived both the broad tuning and the fine tuning from the same cam motion, while my invention runs thru the major range with a steady, uni-control drive for all the units, while the individual cams operating in separate correctional trains from the same unicontrol, apply the various positive and negative corrections by differential actions. The

difference in result may be readily seen from a practical example. Take two. receivers hav ing cams of the same size or travel and formed with the. same limits of precision say for example the amplitude of the cam travel is one inch and the cams are. formed to a precision of one hundredth of an. inch... The operating precision of the cam is then one per cent. Applied in the former manner,this would give a control down to one per cent of the breadth of the whole broadcast range, no better than the. ordinary uni-control, where the, individual differences to beamrected are only in the order of about one per cent. In my invention the same z'nnount'of cam motion could be concentrated on applying the corrections, where the total scope of the zone, to be operated in is only about one per cent of the broadcast zone; the precision would then be one per cent of one per cent. In other words, the former systems would give a precision of one-hundredth, while my method, with the same workmanship, gives a precision of one-ten thousandth. The advantages of my method in any resonating system where a quick succession of precise results from a single control is desired, will be ap parent to those skilled in the art.

It will be understood that the apparatus illustrated in the drawings is one of the preferred embodiments of my invention and has been used merely to facilitate the explanation of the principle of my invention and that modifications may be made, and that I therefore desire that no limitations be placed upon my invention other than those imposed by the scope of the appended claims.

What I claim as new and. desire. to secure by Letters Patent of the United States is as, follows:

1. In an, electrical tuning system, the combination of two or more stages each includmg cooperating elements whose position relative to each other determines the tuning, uni control means, for smoothly changing the relative positions of the cooperating elements within the various stages simultaneously to effect the broad tuning, separately calibrated correctional means for one or more of said stages operating differentially to vary the relative position of the cooperating elements to accord with the individual corrections necessary to obtain accurate, resonance, said correctional means being also operated by said uni-control, whereby separate small corrections may be superposed differentially on the broad tuning simultaneously with the operation of the uni-control to afiord a succession of accurate resonances in tuning from a uni-control.

2. In an electrical tuning system, the combination of two or more resonance devices of slightly diflerent characteristics capable of being tuned to substantial resonance from a single control so as to proceed progressively with substantial selectivity thru a broad range, uni-control means for operating said devices, micro-correctional means for the several stages including cams calibrated for r' a micro-correctional range, said micro-cor- 'rectional means being also operated by said uni-control means, whereby a succession of accurate resonances may be obtained by operating the uni-control.

3. The method of tuning to resonance over a broad range an electrical system having two or more circuits each provided with adjustable resonance means, comprising the steps of effecting simultaneously an approximately uniform adjustment of said resonance means to maintain approximate broad tuning of said circuits, and effecting, simultaneously with said approximate adjustments, a separate, further adjustment of the resonance 2 means of one or more of said circuits, to

correspond with said approximate adjustments to correct the errors thereof and maintain precise tuning thruout said range.

4. In an electrical tuning system, the

method of tuning to resonance two or'more circuits having groups of cooperating elements whose relative position determines the tuning, including the steps of simultaneously adjusting the groups to maintain approximate resonance thruout different points in the broad tuning range and at the same time adjusting at least one element in said groups with respect to its cooperating element to continuously maintain accurate resonance,

- the last mentioned adjustment being progressive or retrogressive within a relatively narrow range while the first mentioned adjustment is progressive.

5. In an electrical tuning system having groups of resonance elements of irregular characteristics to be tuned to accurate resonance in successive positions with means for efiecting the broad tuning of the groups in unison with one order of precision and individual irregular correctional devices having a higher order of precision for fine tuning, the method of maintaining successive settings in accurate resonance which comprises actuating the correctional devices simultaneously in strict accord with the progression of the broad tuning and with an order of precision higher than that of the broad tuning, and combining the correctional action with the broad tuning action diiierentially within the groups.

In testimony whereof I afiix my signature.

HAROLD N. BLISS. 

